Aluminum brass alloy



perior resistance to Patented June 4, 1935 UNITED STATES ALUMINUM BRASS ALLOY John B. Freeman, Jr., Cheshire, Conn., assignor to The American Brass Company, Waterbury, Conn., a corporation of Connecticut No Drawing. Application October 30, 1934,

Serial No. 750,075

8 Claims.

This invention relates to a brass alloy, and has for an object to provide such an alloy which has superior corrosion resistance, and more particularly to produce a brass alloy which has sudezincification.

Brass alloys are widely used for the construction of equipment subject to corrosion by corrosive solutions, such as sea water. For example in the manufacture of condensers, condenser tubes, ferrules, and the like for use in corrosive waters such as sea water, copper zincalloys of the well known compositions of so-called Muntz metal, Admiralty metal and aluminum brass are extensively used. These alloys have the following approximate compositions Muntz metal copper, 40% zinc.

Admiralty metal copper, 29% zinc, 1% tin.

Aluminum brass 76% copper, 22% zinc, 2% aluminum.

In service all of these alloys are subject to a type of corrosion failure known commonly as dezincification. This dezincification occurs due to a rather complicated electrolytic action which results in a gradual removal of the zinc from the surface and deposition of a more or less spongy copper deposit in place of the alloy. This dezincification causes a gradual weakening of the tube and eventual failure in service. The dezinciflcation occurs sometimes in a more or less uniform manner over the surface of the tube,

and at other times in isolated areas where the dezincification is intensified, eventually penetrating the tube wall and causing failure by leaking. This latter type of dezincification is commonly referred to as plug type dezincification.

Tests and experience have shown in tubes having composition of the aluminum brass type that dezinciflcation of the plug type may occur under some conditions. This type of dezinciflcation is more serious than a uniform general dezinciflcation and militates against a broad more general use of the alloy.

I have found that if a small amount of arsenic is caused to be present in the alloy that dezincification is markedly reduced, and in particular dezincification of the plug type? is greatly reduced in service. Only very small amounts of arsenic are required to prevent, or at least to greatly reduce or retard this dezincification so that the tubes and similar parts, for example in condensers, give much longer service than tubes and other parts made from a similar alloy in which the arsenic is not present.

Thus for example, I have found that an alloy of the approximate composition of 76% copper, 2% aluminum, 0.04% arsenic, and remainder zinc does not dezincify in the manner in which alloys of similar composition but without arsenic will dezincify. I have also found that the ranges of the various elements may vary. Thus I have found that amounts of less than 0.01% arsenic and as low as 0.005% arsenic are beneficial, but I prefer to use larger amounts, and it 10 may be as high as approximately 0.5%. In other words the range for arsenic may be from 0.005% to about 0.5% although the optimum amounts for best results appear to be from about 0.02% to about 0.06% arsenic. These amounts of ar- 15 senic may be used and will give improved corrosion resistance and inhibit dezincification in aluminum brass alloys in which the copper varies from about 70 to about aluminum from about 0.5% to about 6.0%; and the. remainder 2o zinc, although the preferred alloy is approximately from '75 to 77% copper; approximately 1.5% to 2.5% aluminum; and the remainder zinc.

Having thus set forth the nature of my invention what I claim is:

1. A brass alloy containing from about 70% to 85% copper, 0.5% to 6.0% aluminum, 0.005% to 0.5% arsenic, and the remainder zinc.

2. A brass alloy containing approximately from 75% to 77% copper, 1.5% to 2.5% alumi- 30 num, 0.02% to 0.06% arsenic, and remainder zinc.

3. A brass alloy containing approximately 76% copper, 2% aluminum, 0.04% arsenic, and remainder zinc.

4. An alloy composed of copper 76%, zinc 21.9%, aluminum 2%, and arsenic .1%.

5. A condenser tube made of a brass alloy containing from about 70% to 85% copper, 0.5% to, 6.0% aluminum, 0.005% to 0.5% arsenic, and the 40 remainder zinc.

6. A condenser tube made of a bras alloy containing approximately from 75% to 77% copper,

1.5% to 2.5% aluminum, 0.02% to 0.06% arsenic, 45

and remainder zinc.

7. A condenser tube made of a brass alloy containing approximately 76% copper, 2% aluminum, 0.04% arsenic, and remainder zinc.

8. A condenser tube made of an alloy com- 50 posed of approximately 76% copper, 21.9% zinc, 2% aluminum,'and 0.1% arsenic.

JOHN R. FREEMAN, J3. 

